Currently, there is no form of display that allows objects to be imaged “in thin air.” There are various forms of stereoscopic or holographic display which allow an observer's two eyes to perceive two different images, as long as the observer is looking into a display screen.
There are also swept-screen volumetric displays, in which rapidly successive images are projected upon a physically rotating screen which repeatedly sweeps through a volume. In this case a volumetric image composed of points of light is directly formed in space, visible by multiple observers. The entire device needs to be enclosed in a transparent dome, for safety. Alternatively, some volumetric display devices employ two laser beams of different frequencies, focused into a cubic volume that is filled with a photo-responsive material. At any given moment, the material visibly glows at that point within the cube where the two laser beam foci meet. By optically scanning the two beams through this material, a volumetric image can be formed within the cube.
But the display described in FIGS. 9 and 10 is the first which enables the sort of scenario popularized by such films as “Forbidden Planet” and “Star Wars.” In the display devices posited in those movies, an animated figure is imaged directly in the air between them, with no need for a projection screen.
Such a display, for example, allows two or more people to hold a conversation, while discussing an animated figure or other object of interest that can be floating directly in the air between them. Observers can freely pass their hands through the display volume.